The current study demonstrates a sophisticated and environmentally friendly synthesis of zinc oxide nanoparticles (ZnO-NPs) for a range of biological and environmental applications using Monotheca buxifolia as a bio-source. At the nanometer scale, a simple aqueous extract from Monotheca buxifolia was used to convert Zn into stable elemental zinc (Zn⁰). With an average size of 45.8 nm and a spherical shape, the NPs were stable and pure. The nanoparticles studied here were tested in vitro for bactericide, fungicide, biocompatibility, leishmaniasis, anti-diabetic effect, antioxidant effect, and anti-Alzheimer’s effect. According to our results, Monotheca buxifolia mediated ZnO-NPs are highly effective against spore-forming fungal strains and MDR bacterial strains. All examined bacterial isolates of UTI (urinary tract infection) were resistant to non-coated antibiotics; however, adding 1% of the produced ZnO-NPs to the treatments increased their bactericidal activity significantly. The NPs also showed dose-dependent cytotoxicity against Leishmania tropica parasites, with an LC50 of 248 μg/mL for promastigote parasites and 251 μg/mL for amastigote parasites. In addition, a significant inhibition of α-glucosidase, α-amylase, butyrylcholinesterase (BChE), and acetylcholinesterase (AChE) was discovered, indicating anti-Alzheimer’s and anti-diabetic effects. The biocompatibility of the particles with human red blood cells was also observed. Due to their environmentally friendly production, biological safety, and exceptional physicochemical properties, ZnO-NPs could be used as a new competitor for several biological and environmental applications.

The apple is the most widely used fruit globally. Apples are more prone to fungal spoilage, which leads to browning and subsequent changes in their flavor and texture. Browning is also caused by the tyrosinase enzyme. By inhibiting tyrosinase initiation and fungal spoilage in fruits, the natural flavor and texture of fruits can be maintained. Biogenic NPs can act as antioxidants to inhibit tyrosinase and due to oxidative stress, it also catalyzes the deformation of fungal hyphae and spores. Nanotechnology is a research hotspot that has gained considerable interest due to its potential inferences in biosciences and food preservation technology. The present study aims to use biomass from the Fagonia cretica to create bio-inspired manganese oxide MnO₂ NPs and to evaluate its bio-catalytic potential for antifungal anti-browning through the inhibition of tyrosinase and its antioxidant potential for preserving apple flavor and texture. The green synthesized nanoparticles were extensively analyzed using UV spectroscopy, XRD, SEM, EDX, and FTIR techniques. Moreover, the synthesized manganese oxide nanoparticles (MnO₂ NPs) were evaluated for their bio-catalytic potential as anti-fungal and anti-spoiling agents. The values of antifungal activity among all the samples were 14.2 ± 86 mm, 8.9 ± 6.0 mm, 17.7 ± 1.26, and 20.7 ± 4.38 mm for Penicillium expansum, Monilinia fructigena, Penicillium chrysogenum, and Aspergillus oryzae at 200 µg/well, respectively. Moreover, the biogenic NPs were evaluated for their anti-browning potential through the inhibition of tyrosinase. MnO₂ NPs have been shown to have considerable inhibitory effects on tyrosinase up to 64.8 ± 0.16 at 200 µg/mL and (27.2 ± 0.58) at 25 µg/mL. Biogenic MnO₂ NPs can also act as antioxidants to inhibit tyrosinase and fungal growth by the formation of free radicals that damage the fungal hyphae and, as a result, slow down browning. The maximum DPPH free radical scavenging activity was 74.5 ± 0.39% at 200 µg/mL, and the minimum was 12.4 ± 0.27 at 25 µg/mL. The biogenic MnO₂ NPs are biocompatible and play a potent role in maintaining the flavor and texture of apples.